Mixed small cell neuroendocrine carcinoma and squamous cell carcinoma covered by tubulovillous adenoma in the rectum: a case report and detailed molecular analyses

Abstract

Background Previously, only six cases of mixed neuroendocrine-non-neuroendocrine neoplasm (MiNENs) with squamous cell carcinoma (SCC) component have been described in the colorectum, and the molecular landscape of MiNENs is also poorly understood. Herein, we present a unique case in which the SCC developed as a component of a MiNEN in the rectum. Case presentation The patient was firstly diagnosed as rectal small cell neuroendocrine carcinoma (SCNEC) covered by tubulovillous adenoma, and then mixed SCNEC and SCC in the same site 6 months later. Representative samples from the three histologic subtypes were then sent for next-generation sequencing (NGS) separately. Multiple liver metastases occurred in the following month after the last surgery. The patient died of ketoacidosis 1 year after initial diagnosis of the tumor. Conclusion This is the first report of this exceedingly rare tumor type to include NGS of the 3 separate morphological entities. Our findings may expedite the understanding of combined tumors in the colorectum.

Small Cell Carcinoma of the Rectum Associated With a Tubulovillous Adenoma: An Atypical Case Presentation

“…This case of small cell carcinoma of the rectum, arising in association with a tubulovillous adenoma, illustrates a rare occurrence in colorectal cancer pathology. The initial diagnosis of a benign adenoma through colonoscopy, followed by the unexpected finding of a malignant small cell carcinoma post-surgery, highlights the need for vigilance in cases with atypical presentations [ 9 , 14 ]. The presence of hepatocellular carcinoma (HCC) in this patient added a layer to the clinical picture, though it is important to note that the management of the rectal carcinoma was considered independent of the HCC.…”

“…When it occurs in the rectum, it constitutes a small fraction of colorectal malignancies [ 12 ]. The rare incidence of rectal small cell carcinoma presents unique challenges in diagnosis and management, making each case a subject of clinical interest [ 13 , 14 ].…”

Uso de la Plataforma de Acceso Transanal Gelpoint® Path para la Resección Local de Neoplasias del Recto

“…De acuerdo con la Organización Mundial de la Salud (OMS) el cáncer de colon y recto representa el 19,3 % de todas las neoplasias malignas a nivel mundial, con un 47 % de mortalidad anual (1). El riesgo de padecer cáncer rectal es de 1 en 26 para mujeres y de 1 en 23 para hombres; entre los tumores del recto encontramos en su gran mayoría adenocarcinomas (2).…”

“…Los adenomas son lesiones no cancerosas que se desarrollan a nivel de colon y recto, compuestos por epitelio displásico de la mucosa. Estas lesiones se clasifican histológicamente en adenomas tubulares, adenomas tubulovellosos (pólipos velloglandulares) o adenomas vellosos; la mayoría asintomáticos y descubiertos incidentalmente (2). El riesgo de malignización de los adenomas con displasia de alto y bajo riesgo es de 27 % y 5 %, respectivamente a los 15 años y pólipos < 1 cm se espera que se conviertan en adenocarcinoma invasivo, a los 10 años (2).…”